Grinding machine



Patented Aug. 25, 1925.

UNITED STATES PATENT OFFICE.

JOHN A. SMITH, OF BELLEVUE, KENTUCKY, ASSIGNOR TO THE UNITED STATES ELECTRICAL TOOL COMPANY, OF CINCINNATI, OHIO, A CORPORATION OF OHIO.

GRINDING- MACHINE.

Application filed August 24, 1923.

To all whom t may concern:

Be it known that I, JOHN A. SMITH, a citizen of the United States, and residing at Bellevue, in the county of Campbell and State of Kentucky, have invented new and useful Grinding Machines, of which the following specification is a full disclosure.

This invention relates generally to grinding machines, and particularly to a safety device applied thereto, which device is designed to prevent actuation of the power control lever for operating the wheel at dangerous velocities.

The device is connected with a motor control` lever, and is operable to permit rotation of the wheel, only at predetermined velocities proportional to wheel radius, and to allow increase of velocity only when the length of the radius of the wheel has been correspondingly reduced, as by wear of the wheel. As the wheel wears, the device provides for the operation of the power contro lever to obtain increase of velocity proportional to such wear.

There is a velocity at which the wheel may be safely operated without danger of wheel fracture, an object of this invention being to prevent operation of the power control lever to obtain velocities over andV above the safety limit. As herein shown, a motor is operated through a rheostat, controlled by a hand lever, and the rotative velocity of the motor is increased by operating said lever in step-by-step movements for cutting in of rheostat resistance. By the use of my device, a factor of safety is added to the operation of the grinding wheel, inasmuch as the device will prevent operation of the lever to give unsafe wheel velocity, and yet allow for an increased velocity proportioned to decrease in radius of the wheel, due to wear.

Another object of the invention is the provision of means for locking the wheel or motor shaft against rotation when it is desired to remove the grinding wheels.

Gt-her objects and certain advantages will be more fully set forth in the description of the accompanying drawings forming a part of this specification, in which:

Figure l is an end elevation of a grinding machine having my improved safety device applied thereto, and

Figure 2 is a rear elevation.

The machine herein, which represents one Serial No. 659,192.

commercial type of grinder, has the base 1 provided with aligned bearings 2 between which bearings is disposed a motor 3 having a shaft 4 extending through andbeyond each bearing 2, each extension having thereon, 1n this instance, a grinding wheel 5. Although a double arrangement of wheels is herein shown, the invention may be applied to machines having a greater or less number of wheels. A circular sheet metal element, in this instance, a guard 6, surrounds each wheel concentric therewith, and spaced therefrom to allo-w free rotation of the wheel, and also sufficiently spaced from the wheel to allow of limited translation relative thereto, 1n a direction at right angles to the long axis of the drive shaft. For this purpose each guard is provided with an extension 7 having suitable sliding connection with respective horizontally disposed ways 8 upon brackets 9, attached to the base l. The

1 guards are open at the front through a portion of their circumference to permit of access to the wheel for grinding purposes, and at that edge dening the top of the opening is placed an adjust-able guard linger 10, extending therebeyond and provided for the purpose of engagement with the wheel when the guard is horizontally translated in a rearward direction and acting as a stop, and as a signal to the operator. Rearwardly of the base in horizontally aligned bearings 15 is disposed a control shaft 16 having crank arms 17 at relatively opposite ends, the outer end of said crank arms being respectively pivoted to links 18 in turn pivoted to the corresponding extensions 7 of the guards. A control or operating hand lever 20 is attached to the shaft for rocking the same. Non-rotatively attached to the shaft is an arm 2l having pivotal connection, as at 22, with the link 23, which link is in turn pivoted to a rheostat switch lever 24, pivoted as at 25 to the rheostat panel 26. The rheostat points are indicated at 27 and are suitably connected in the usual manner in the power line circuit, the connections not herein shown.

In the arrangement provided, step-bystep increment of motor speed may be obtained by operating the lever in the direction shown by the arrow, which correspondingly operates the rheostat lever 24 to increase resistance and correspondingly increase motor speed or shaft rotation.

Should the operator attempt to cut in greater resistance and correspondingly increase motor speed to a dangerous extent, or beyond that for which the device is set, the guard or cover will be translated rearwardly and the finger l0 will engage the wheel to prevent further lever actuation, and to give an audible signal calling attention of the operator to the fact. As the radius of the wheel is decreased by wear and the space between the outer periphery of the wheel and the inner face of the wall of the guard is increased, greater translative movement of the guard is permitted, as well as corresponding inward movement of the rheostat lever, to additionally increase resistance and increase motor speed.

The shaft l has keyed thereto a disc or wheel 30, notched as at 31. Adapted for engagement with the notches of said wheel is a push pin 32 mounted in the motor casing 33, said pin being notched as at 34C, and said notches being engageable by a spring-pressed pawl 35, whereby the pin may be engaged and disengaged from the notches of the disk 30 and forcibly but yieldably held in such engaged or disengaged position. The shaft 4 may thus be held against rotation when the grinding wheels are to be removed or when new wheels are to be attached to the shaft.

The safety device positively prevents rotation of the wheel at dangerous velocities and only permits of operation of the wheel at safe velocities, proportional to wheel radius.

Having described my invention, I claim:

l. In a. grinding machine, a shaft, a grinding wheel upon said shaft, a translatable element engageable with said wheel, a motor speed control device, and means operably connecting said control device and translatable element.

2. In a grinding machine, a motor, a motor shaft, aI grinding wheel upon said shaft, a cover concentrically surrounding said grinding wheel and movable transversely to the grinder wheel axis into contact with the wheel, a motor speed cont-rol device, means for operating said device, and means operably connecting said cover and said motor speed control device operating means, whereby engagement of the cover with said wheel will prevent ope ation of said power control means.

3. In a grinding machine, a motor, a shaft for said motor, a grinding wheel on said shaft, a cover concentrically surrounding, spaced from said wheel and having an extension thereon engageable with said wheel, a motor speed control device for obtaining step-by-step increment of motor speed, means for controlling said speed device, and connections between said control means and cover, whereby operation of said control is prevented by engagement of said cover with said wheel.

4. In a grinding machinet a motor, a motor shaft, a grinding wheel upon said shaft, a cover concentrically surrounding said grinding wheel spaced therefrom and translatable relative thereto in a plane at a right angle to the axis of said sha-ft, a motor speed control device, means for operating said device, and connecting means between said cover and motor speed control device, whereby actuation of said motor speed control operating device is prevented.

5. In a grinding machine, a motor, a. shaft for said motor, a grinding wheel upon said shaft, a cover spaced from and concentrically surrounding said wheel, and translatable relative thereto, said cover having an extension engageable with said wheel, a motor speed vcontrol device for obtaining step-by-step increment of motor speed, a lever for controlling said control device, and connections between said lever and cover, whereby operation of said lever is limited by engagement of the cover with the wheel.

6. In a grinding machine, a driven shaft having a grinder wheel fixed thereon, speed change transmission means and a controller therefor for driving and controlling the speed of the shaft and wheel, a. grinder wheel hood provided with an opening through which access to the wheel is given, the hood movable transversely to the grinder wheel axis into contact with the wheel and connecting with said controller, for hood movement with the controller actuation to limit the controller speed changing actuation by hood contact with the wheel, and a definite speed changing control for determined grinder wheel diameters.

7. In a grinding machine, a motor, a mot-or shaft, a grinding wheel upon said shaft, a translatable guard concentrically surrounding said wheel and spaced therefrom, a rheostat for controlling said motor, having a switch lever and a control lever operatively connected with said switch lever and said guard to limit actuation of said lever to prevent excessive motor speed increase.

8. In' aI grinding machine, a rotative grinding wheel, a transmission cont-rolling lever for controlling the veloctiy of the grinding wheel, and a guard covering the wheel slidably supported and movable transversely to the axis of the wheel and connecting with said lever, said guard having an opening for grinding access to the wheel providing an edge engageable with the periphery of the wheel for limiting the transverse movement of the guard in a rearward direction and thereby limiting the movement of said controlling lever.

In witness whereof I hereunto subscribe my name.

JOHN A. SMITHo 

